Well, let’s say tampering with the bootloader is dangerous. I have seen some reports where people ended up with an unusable phone - though relocking bootloader seems to be more critical then unlocking …
Yes, exactly, relocking bootloader is the critical step (but we’re getting quite off-topic here! 
).
The FP6 just dropped in.
I’ll give it another pause through the rest of the year as I will attend 39c3 and hanging out there at the buildup.
No use getting the new one in any trouble.
I am on FP6 since 12.04.26, finally got all apps, messengers and data shifted without using some cloud, even most settings are there. The backup process was very long with low data rates though.
Used Package Manager and Open_Android_Backup_v1.2.0_Bundle.zip.
A few things are missing, some due to the change from Android 13 to 15, as the long sreenshot options are gone. Couldn’t find the place where my old background was saved either, but found a workaround using a screenshot from FP3 to install on the new one.
Glad you managed the leap
Extended screenshots can be made (if the screen content allows) but only if you use Power + Volume -.
It’s not currently possible to extend screenshots made from the Recents list, as far as I know.
Using Power + Volume - leads to a screenshot I can edit or share but it will be same size as the screen. I used it much for the battery usage list. On 15 it seems not available, which is a pity.
As I said above, it depends on the screen content. For example you can obtain an extended (but not complete) screenshot of settings>apps>all apps
or lists of folders and files in a file manager.
Your FP6 should be on A16, but the extended screenshot worked with A15 too I think.
Well, in Settings → Battery → Battery usage you have a list much longer than the screen. On Android 13 I could capture the whole list in a long screenshot.
Now that is impossible. So, in order to show something specific, e.g. app-usage, you have to take multiple shots and combine them.
I wonder why these decisions are drawn, read already lots of posts who laothed this either.
I am running e/OS, and that happens to be on 15 still.
Probably your best option is to discuss the question in the Murena forum.
The extended screenshot is available with stock FPOS.